1. Field of the Invention
This invention relates to optical elements and methods of making them by using micro-jet printing methods to precisely control the type, position and amount of polymer deposited onto a substrate.
2. Description of the Related Art
Optical elements such as eyeglass lenses are typically made by casting, grinding and/or polishing blanks made from glass or plastics such as polycarbonate and polyethylene glycol diallyl dicarbonate (CR39). However, lenses made by these fabrication techniques are only capable of correcting relatively simple vision problems. Other fabrication techniques have been developed to address more complex vision problems, but these techniques are uneconomical because they are relatively complicated and not well-suited for mass production.
Lens elements with a spatially varying index of refraction are known, see, e.g., U.S. Pat. No. 6,089,711. The material for the fabrication of such lenses can be made by a variety of processes such as sol-gel, infusion, and diffusion. However, these fabrication techniques produce lenses having a radial gradient profile in which the index of refraction increases or decreases monotonically across the radius of the lens because the gradient is obtained by a diffusion process. These fabrication techniques are inapplicable to the manufacture of lenses in which the index of refraction at any particular point can be specified in a controlled manner to produce a radially non-monotonic refractive index profile. Arrays of microlenses have been made by irradiating a photopolymerizable or photocrosslinkable substance with laser light having an uneven distribution of intensity, see U.S. Pat. No. 5,998,096. However, the presence of unreacted photoreactive substances remaining within the irradiated article often presents stability problems.
Micro-jet printing methods have been reported which are said to be capable of printing arrays of microlenses onto a substrate, see U.S. Pat. Nos. 5,498,444; 5,707,684; and W. Royall Cox et al., “Micro-Optics Fabrication by ink-Jet Printing,” Optics and Photonics News, pp. 32-35, June 2001. Methods have also been reported for modifying the surface of lenses to correct for optical aberrations, see U.S. Pat. No. 6,086,204. However, such methods seek to control optical properties by controlling the thickness of the lens, rather than by controlling the refractive index of the material from which the lens is made. Methods have also been reported for varying the effective index of refraction by using lithographic methods to produce very small bore holes in the lens material, see U.S. Pat. No. 5,585,968.